离子液体@分子筛核壳催化剂设计及其在C4烷基化反应中的应用

The alkylation between isobutane and butene catalyzed by strong acid is an effective method for the production of clean gasoline blending component with high octane number. Ionic liquids (ILs) as a kind of environmental friendly catalyst, is considered as an alternative to the traditional concentrated sulfuric acid and hydrofluoric acid catalyst with respect to activity and selectivity. In order to improve the utilization of ionic liquid and reduce cost, the supported ionic liquid catalyst (SILCs) has become a new research direction. However, the active center is fixed on the surface of the support in SILCs, which leads to the increase of the activation energy of the hydrid transfer in the alkylation reaction, finally resulting in the catalyst deactivation due to plugging channel with the polymer formed. In this project, we intends to create an ILs@ molecular sieve core-shell catalyst like a fresh egg. Firstly, ILs is filled into the cavity of the inert molecular sieve hollow spheres by physical forced penetration, then shrinking the pore size of molecular sieve membrane using a low temperature chemical vapor phase deposition method to lock ILs in the cavity jail. This novel alkylation catalyst takes the advantages of both solid and liquid catalyst and it is a solid in macroscale and liquid in microscale. Most important, it has the free active sites as in the pure ionic liquids’ phase, which means lower activation energy of the hydrid transfer. From the view of mesoscale, the transport diffusion and microscopic kinetics behavior will be investigated systematically in the confined space for the alkylation reaction catalyzed by this novel catalyst. The effect of spatial scale of the molecular sieve hollow spheres on the physical and chemical properties of ILs and its catalytic completive mechanism between the rate controlling step and side reactions will be revealed through experimental and theoretical investigations, as well as the controlling method to adjudge the composition of alkylation gasoline. It provides new ideas to develop an efficient and environmentally begnin catalyst and scientific basis for the production of clean gasoline with green process.

强酸催化的异丁烷/丁烯烷基化是合成高辛烷值清洁汽油调和组分的重要反应。离子液体（ILs）是一种有望替代浓硫酸和氢氟酸的环境友好型烷基化催化剂。为了提高ILs的利用率，负载离子液体催化剂（SILCs）成为研究趋势。但是SILCs中固定的活性中心使烷基化反应中氢负离子转移活化能升高，易形成聚合物堵塞孔道造成催化剂失活。本项目拟设计新型离子液体@分子筛核壳烷基化催化剂。以强酸性复合离子液体为活性组分，核壳结构的分子筛小球为载体，采用大孔灌注-缩孔锁定的方法将离子液体以液态的形式锁定在载体大孔空腔“牢笼”中，保证离子液体活性中心的自由度。深入研究介尺度限定空间内ILs催化烷基化反应的传递规律和微观动力学；结合实验和理论计算，揭示介观尺度上球腔尺寸对ILs的理化性质及催化氢负离子转移和副反应的竞争机理的影响规律。为开发高效环境友好的烷基化催化剂，实现清洁汽油绿色生产提供新思路和科学基础。

对于设计高效离子液体@分子筛核壳催化剂难度较大，如何设计离子液体、提高离子液体稳定性和利用率，如何稳定碳正离子、抑制聚合、促进氢负离子转移，以及介尺度限定空间内离子液体纳微结构、催化活性中心的存在形式、稳定性、物化性质和空腔尺寸之间的关系是研究的关键。本项目设计了两类新型的离子液体催化剂1）相转移类离子液体催化剂，可以增强体系的相容性，促进传质传热，加速反应，2）质子酸类离子液体协同催化体系，有利于稳定碳正离子、抑制聚合、促进氢负离子转移。对于分子筛载体，设计合成了稀土元素改性合成多级孔分子筛。采用大孔灌注-缩孔锁定的方法将离子液体以液态的形式牢牢锁定在载体的大孔空腔“牢笼”中，实现真正意义上的液体催化剂多相化，保证离子液体催化剂活性中心的自由度。进一步研究介尺度限定空间内离子液体纳微结构、催化活性中心的存在形式、稳定性、物化性质和空腔尺寸之间的关系；探索受限空间内反应的传递规律和微观动力学；结合实验和理论计算，深刻认识其催化反应机理。获得一类适用于异丁烷-丁烯烷基化反应的高效离子液体@分子筛核壳催化剂。为开发高效环境友好的烷基化催化剂，实现清洁汽油绿色生产提供了新思路和科学依据。